The present invention relates generally to the field of virtual private networks, and more particularly to a method of and system for providing a virtual private network in which a portion of each call is transported through an internet protocol network.
Some larger organizations with farflung sites and locations use virtual private networks (VPNs) as an alternative to traditional long distance services for their intra-organizational telephone communications. Virtual private networks are created within the public switched telephone system but they provide a communication system that appears from the users prospective to be private.
Referring to FIG. 1, there is shown a simplified block diagram of a virtual private network. An intra-location telephone system includes a plurality of telephones 11 operably connected to a private branch exchange (PBX) 13. As is well known to those skilled in the art, several or even hundreds of telephones may be operably connected to PBX 13.
PBX 13 provides intra-site communication between telephone and other telephones at the site. Additionally, a user of a telephone 11 may make a local or long distance call outside of the location by entering a digit, such as xe2x80x9c9xe2x80x9d, to obtain an outside line. Additionally, a user of telephone 11 may make a VPN call by entering another digit, such as xe2x80x9c8xe2x80x9d, to reach a member of the organization at another location. The other location may be in a separate city, state, or even country. Typically, VPN numbers have the appearance of local seven digit telephone numbers. A three digit prefix number identifies a location and the remaining four digits identify a telephone within the location.
In the example of FIG. 1, a user of telephone 11 at a location located in, for example, California, wishes to place a VPN call to a telephone 15 located at a site of the organization in, for example, New York. The telephones 15 of the site in New York are operably connected to a PBX 17 that services the site. For purposes of illustration, the VPN number associated with telephone 15 is 555-1234. To initiate the call, a user takes telephone 11 off hook and receives a dial tone from PBX 13. The user enters xe2x80x9c8xe2x80x9d to identify the call as a VPN call and receives another dial tone. Then, the user enters the digits 555-1234. PBX 13 forwards the call to a switch 19 of a public switched telephone network (PSTN) 21 over a direct access line (DAL 23). Switch 19 is identified in PSTN 21 by a unique originating switch identifier (OSID). DAL 23 is identified by an originating truck group (OTG) identifier. When switch 19 receives the dialed digits on the DAL 23, it must consult a service control point (SCP) 25 for routing instructions. SCP 25 uses the OSID and the OTG to determine the identity of the VPN customer and provides routing instructions to switch 19 based on the customer identification and the dialed digits. Switch 19 routes the call through PSTN 21 to an appropriate terminating switch 27. Switch 27 is operably connected to PBX 17 to complete the call to telephone 15.
One of the problems with VPN service is that the public switched telephone network does not extend reliably to all parts of the world. Because of the unreliability of the PSTN in certain parts of the world, certain locations of organizations particularly, those located in developing nations, are unable to use VPN services.
Recently, organizations have begun to build and use packet switched data networks, such as private intranets and the Internet itself, for mission critical communications. Even in regions without reliable access to the public switched telephone system, organizations have built or have gained access to robust high speed data networks for the transfer of data and electronic communications, such as e-mail, between locations.
It is an object of the present invention to provide a system that extends VPN services through data networks, such as private intranets and the Internet.
The present invention provides a virtual private network (VPN) that includes an internet protocol (IP) network and a public switched telephone network (PSTN). An egress enterprise gateway is operably connected to the IP network. The egress enterprise gateway is operably connected to a switch of the PSTN through a direct access line (DAL). The set-up signaling for virtual private network calls and the calls themselves are transported across the IP network and the PSTN through the DAL. An intelligent layer in the IP network has the ability to route IP network originated calls to a traditional PSTN DAL.